Ethernet Advancements Help Deliver Integrated Plantwide Network Architectures

  • June 07, 2011
  • Feature
June 2011
Industrial Layer three switches further expand Ethernet’s flexibility  
By Gregory Wilcox, Mike Hannah and Mark Devonshire of Rockwell Automation
Was it just over ten years ago that many engineers scoffed at the idea of using Ethernet in the manufacturing environment for both control and information applications?
Industry experts predicted that node cost, determinism issues and security risks would prohibit Ethernet’s growth into manufacturing, but fast forward to today, and it’s clear that this prediction hasn’t held true. The swift rise and widespread industry adoption of Ethernet has outpaced its networking counterparts and is a key factor in the adoption rate of EtherNet/IP – the world’s leading industrial Ethernet network.
The Rise of Ethernet
To understand how EtherNet/IP made its fast ascent, one must first take a quick look back at how networking technology evolved. Just over a decade ago, the drive to integrate the manufacturing enterprise from the simplest device to the highest-level information system represented a task that no one network could manage. Consequently, plant floors used multiple networks to transfer different types of data and handle the mix of requirements for discrete, process, batch, motion and safety applications. Meanwhile, standard Ethernet expanded rapidly in the commercial world. With an installed node base numbering in the billions, manufacturers began to see the promise it held for integrating plantwide network architectures, especially as key advances removed barriers to using the technology on the factory floor. These advancements included increasing the network’s speed from 10M to 100Mbs, adding collision detection, and the introduction of full duplex and managed switch technology, to name a few.
With the expanded capability of Ethernet and the promise it held to linking the plant floor to the business enterprise, manufacturers began to look into the various industrial Ethernet protocols. Their conclusion? Networks using standard Ethernet and TCP/IP, such as EtherNet/IP, have little difficulty integrating with the commercial/IT environment and can consequently act as the technology enabler for the convergence of manufacturing and enterprise-level networks. Also, EtherNet/IP integrates seamlessly with other network technologies, such as DeviceNet and ControlNet, to round out the converged network infrastructure.
All three networks share ODVA’s Common Industrial Protocol (CIP). This enables end users to integrate different systems together without the need for gateways or proxies, which increase complexity due to extra configuration and programming. This also permits increased flexibility, assures compatibility and offers ease of device integration into new and legacy systems while giving manufacturers the power to converge their communications architecture for improved operational efficiency.
By leveraging the economies of scale in a proven commercial technology, EtherNet/IP provides users with the tools needed for manufacturing applications while enabling plantwide and enterprise connectivity for data anytime, anywhere. Using common tools, components and even human assets to support a plantwide network architecture helps increase business agility, reduce training and manpower costs, and improve asset utilization. Ethernet’s expansion into manufacturing enabled the migration from the traditional multitier network model to a more converged model (see Figure 1).
Figure 1: A converged plantwide Ethernet infrastructure effectively manages networks and switches.
Today’s converged network model addresses the mix of applications and various types of data that are transferred within the manufacturing enterprise – namely device, control and large information-based packets. It uses EtherNet/IP as the network of choice for multiple control and information disciplines including discrete, process, motion, safety, and drive control, while leveraging it as backbone to other networks used today in the manufacturing enterprise. Using a single network like EtherNet/IP to tie the networking infrastructure together – from the device to the enterprise zone – provides countless benefits.
Traditional device- or control-level networks limit the number of network device connections while EtherNet/IP can accommodate virtually an unlimited number of devices on the network. This provides users with unsurpassed flexibility in designing networks that accommodate their current requirements while enabling easy, cost-effective expansion in the future. Moreover, IT professionals prefer EtherNet/IP because it uses standard Ethernet rather than a proprietary variation. This means the switches, network management tools and training are compatible, or the same as what they use in the enterprise space.
As a result, building a large, expandable industrial network infrastructure with a single network technology and common components is no longer the question. The new question is “How can I design my infrastructure to meet my needs for segmentation, security, reliability, maintainability and performance, while allowing for added capacity?” 
Effective Traffic Management
Traditional industrial network models force segmentation and traffic management by function and geographic area based on the limited capacity of each individual network. Ethernet, on the other hand, doesn’t have these limits and enables a mix of industrial, commercial and business systems and devices on the same network. While Ethernet’s flexibility and expandability provides great benefits, users who implement a converged Ethernet network must employ best practices and planning to effectively segment and structure the network. Effective design will help ensure correct traffic flow, network performance, security and other attributes that are important in the network’s operation.  
Industrial Layer 3 Switches Further Expand Ethernet Frontier
Designing and deploying a robust and secure network infrastructure requires protecting the integrity, availability and confidentiality of control and information data. At the same time, establishing smaller LANs helps manage these different types of network traffic, while creating domains of trust to limit access to authorized personnel. These practices require a new segmentation methodology.
While users traditionally segmented networks by location, they can now segment by function. That’s because VLANs (virtual local area networks) provide traffic segmentation like separate networks did, enabling users to logically segment areas of control to increase performance and minimize network latency and jitter (see Figure 2).
Figure 2: Layer 2 and Layer 3 managed switches enable users to logically segment areas of control, as shown by the colored groupings.
Once users think beyond traditional geographic boundaries, they can start engineering some truly innovative logical network architectures, freeing network design from the constraints of physical layout. Taking advantage of this new segmentation methodology combines the simplicity and maintainability of many individual networks with the power and flexibility of a single network design.
This is where industrial Layer 3 switching technology plays a vital role in communicating and routing traffic. A Layer 3 switch can route traffic between and across VLANs based on IP addresses. This enables a more flexible segmentation model that directs traffic only to where it is needed.
There are a number of routing protocols that have been developed that allow Layer 3 switches and routers to reliably route packets to their destination based on IP address. These routing protocols allow various devices to communicate and maintain viable routes between each other so that packets can always be forwarded if a viable path exists even as connections or devices fail.
The choice of routing protocol, and the configuration and maintenance of the Layer 3 switches and routers typically raise a point of contention between manufacturing and IT personnel. Control engineers require Ethernet switches to meet the functional and environmental requirements of manufacturing, such as ease of use, maintainability and use in harsh or hazardous locations. Meanwhile, IT professionals prefer Ethernet switches that support their infrastructure and security strategies, and use the same software and programming tools that they already are familiar with. Because EtherNet/IP uses Standard Ethernet and IP services, users don’t need special switches or proxies to route data between VLANs and subnets. In addition, both IT and control engineers work with the tools and products they are comfortable using.
Technology Commonality
Fortunately, advances in industrial Ethernet switch technology are providing the functionality and tool sets that address the needs of both manufacturing and IT. Case in point: The Allen‚ÄëBradley® Stratix 8300™ Layer 3 managed industrial switch from Rockwell Automation. The switch uses the Cisco Catalyst operating system and can be programmed using Cisco’s command line interface (CLI), providing IT engineers with the same programming and configuration tools they already use today.
The Stratix 8300 switch also can be programmed using the Rockwell Software® RSLogix™ 5000 software, a design environment that is very familiar to manufacturing and control engineers.
With its support of inter-VLAN routing and advanced routing protocols, the industrially hardened Stratix 8300 switch allows users to integrate multiple Cell/Area zones across the plant and facilitate secure integration with networks at the manufacturing and enterprise levels.
The industrial hardening and modular port count of the Stratix 8300 offers more freedom to locate the switch closer to the application, and provides an economical solution to create smaller network segments when needed. Its Cisco technology enables the Stratix 8300 to easily complement existing Cisco switches and routers and Allen-Bradley’s Stratix 8000 layer 2 industrial counterparts.
The converged EtherNet/IP model provides manufacturers with increased access to plant-floor data, helping them make more accurate, informed decisions while optimizing internal assets and resources. With all devices connected to the common network infrastructure, network security and access management is simplified. At the same time, having common programming and configuration tools for both manufacturing and IT encourages greater collaboration, allowing them to coexist and work toward the common goals and objectives of their business.

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